```/* nag_3d_shep_interp (e01tgc) Example Program.
*
* Copyright 2017 Numerical Algorithms Group.
*
* Mark 26.2, 2017.
*/

#include <stdio.h>
#include <nag.h>
#include <nag_stdlib.h>
#include <nage01.h>

int main(void)
{
/* Scalars */
Integer exit_status, i, m, n, nq, nw, liq, lrq;
NagError fail;

/* Arrays */
double *f = 0, *q = 0, *qx = 0, *qy = 0, *qz = 0, *rq = 0,
*u = 0, *v = 0, *w = 0, *x = 0, *y = 0, *z = 0;
Integer *iq = 0;

exit_status = 0;

INIT_FAIL(fail);

printf("nag_3d_shep_interp (e01tgc) Example Program Results\n");

/* Skip heading in data file */
scanf("%*[^\n] ");

/* Input the number of nodes. */
scanf("%" NAG_IFMT "%*[^\n] ", &m);

if (m > 0) {
/* Allocate memory */
lrq = 10 * m + 7;
liq = 2 * m + 1;
if (!(f = NAG_ALLOC(m, double)) ||
!(x = NAG_ALLOC(m, double)) ||
!(y = NAG_ALLOC(m, double)) ||
!(z = NAG_ALLOC(m, double)) ||
!(rq = NAG_ALLOC(lrq, double)) || !(iq = NAG_ALLOC(liq, Integer)))
{
printf("Allocation failure\n");
exit_status = -1;
goto END;
}

/* Input the data points X,Y,Z and F. */
for (i = 0; i < m; ++i)
scanf("%lf%lf%lf%lf%*[^\n] ", &x[i], &y[i], &z[i], &f[i]);

/* Generate the interpolant. */
nq = 0;
nw = 0;

/* nag_3d_shep_interp (e01tgc).
* Interpolating functions, modified Shepard's method, three
* variables
*/
nag_3d_shep_interp(m, x, y, z, f, nw, nq, iq, rq, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_3d_shep_interp (e01tgc).\n%s\n", fail.message);
exit_status = 1;
goto END;
}

/* Input the number of evaluation points. */
scanf("%" NAG_IFMT "%*[^\n] ", &n);

/* Allocate memory for nag_3d_shep_eval (e01thc) */
if (!(q = NAG_ALLOC(n, double)) ||
!(qx = NAG_ALLOC(n, double)) ||
!(qy = NAG_ALLOC(n, double)) ||
!(qz = NAG_ALLOC(n, double)) ||
!(u = NAG_ALLOC(n, double)) ||
!(v = NAG_ALLOC(n, double)) || !(w = NAG_ALLOC(n, double)))
{
printf("Allocation failure\n");
exit_status = -1;
goto END;
}

/* Input the evaluation points. */
for (i = 0; i < n; ++i)
scanf("%lf%lf%lf%*[^\n] ", &u[i], &v[i], &w[i]);

/* Evaluate the interpolant using nag_3d_shep_eval (e01thc). */
fail.print = Nag_TRUE;
/* nag_3d_shep_eval (e01thc).
* Interpolated values, evaluate interpolant computed by
* nag_3d_shep_interp (e01tgc), function and first
* derivatives, three variables
*/
nag_3d_shep_eval(m, x, y, z, f, iq, rq, n, u, v, w, q, qx, qy, qz, &fail);

printf("\n");
printf("     i     u(i)      v(i)      w(i)      Q(i)\n");
for (i = 0; i < n; ++i)
printf("%6" NAG_IFMT "%10.4f%10.4f%10.4f%10.4f\n", i, u[i], v[i], w[i],
q[i]);
}

END:
NAG_FREE(f);
NAG_FREE(q);
NAG_FREE(qx);
NAG_FREE(qy);
NAG_FREE(qz);
NAG_FREE(rq);
NAG_FREE(u);
NAG_FREE(v);
NAG_FREE(w);
NAG_FREE(x);
NAG_FREE(y);
NAG_FREE(z);
NAG_FREE(iq);

return exit_status;
}
```